“No matter what happens, I will be right there by your side.” - Tweedledum to his sisterThe relationship that is the most important to Tweedledum is without a doubt the one he has with his sister.
Tweedledum greatly respects and admires Tweedledee, doing everything she wants him to. The only time where he isn't fully listening to what Tweedledee tells him is when he calls her sister on a mission, something Tweedledee does not like.
He also cares a lot about her and worries over her when she is hurt, like in Kiddy Grade when Tweedledee was shot and he took her to safety, instead of going after Éclair, as was their mission, alone and not leaving her side while she was being healed. Also, though usually, Tweedledum does as Tweedledee tells him to there are a few times where he is the one reminding his sister of the matter at hand, like with the Geo-sort bomb.
He also can be rather sensible towards how his sister feels, like when he sensed his siter having doubts about what she is doing like, as they were ordered to use a Virus to have Wirbelwind and Donnerschlag attack Éclair and Lumiere. There are rarely times where he disagrees with sister, but if he does, he is willing to voice his disagreement, like when he has his doubts about using the Windstoß against Éclair, as she was a human.In the end though, he is more loyal to Tweedledee than to the GOTT or GTO, like when he sensed his sister discomfort with their mission, he asked if she wanted to abandon the mission.
When it comes to Tweedledee he also cares less about his own his health and is more than willing to use his own body to protect her, like when Éclair freed herself of Windstoß leading to an explosion and he was shown having protected his sister from the blast with his own body. A similar event happened in Kiddy Girl-And, where he jumped in front of his sister to protect her from an attack from Rubis.
It is hinted that he feels more than just sibling love for his sister, as he get's jealous quickly when she shows interest into someone else and is often blushing around her.
While not directly shown they do seem to be on good terms most of the time.
In the beginning both didn't have much to say to each other and were only acting like co-workers, though Tweedledum didn't seem to like the idea of having to work together with Éclair and Lumieré because his opinion was, that he and his sister didn't need the help. Tweedledum also went as far as to call Éclair and her partner "traitors" as Éclair went against GOTT orders and left the GOTT. When he met Éclair in the elevator shaft as the woman attacked the GOTT, after his sister said that if she surrendered Éclair wouldn't come to harm, he told her that that would only be if she could get the Chief to lift the charge against her. Later though, they're shown to be on good terms, as he was one of the people visitng her as Lumiere was sick and know each other well enough, as Éclair didn't get angry with Tweedledum expressing his hope for Lumiere to get better by saying he wanted a rematch.
He also joined the battle against Alv and the Deucalion and together with his sister used the C-squard to shield Éclair and Lumieré from an attack, as the two of them were defencless at the merci of Alv.
He was shown mourning Éclair's death.
At the end of Kiddy Grade, he was one of the E.S members to visit the baby Chevalier who was Éclair's adopted son.
In Kiddy Girl-and he was one of the E.S members worried about Éclair and tried to stop her from using all of her abilities to stop the planet from exploding because it would kill her.
Initially, Tweedledum showed jealousy towards Lumieré because the attention she got from his sister. Beside that, they aren't shown to have much of a relation beside being co-workers and Lumieré being friends with Tweedledum's sister. He event went as far as to call Lumieré and Éclair "traitors" as she went against the GOTT with Éclair without any troubles. Still, Tweedledum visits Lumieré as she was sick together with his sister and expressed his hopes of her getting better soon again in his own way. All in all, they seem to have a good co-worker relationship in the end.
Eclipse is the Chief of the GOTT and as thus the boss of Tweedledum. They aren't shown to have any interaction on screen. Still Tweedledum seems to respect her as the GOTT Chief.
Alv is a fellow E.S member of Tweedledum. Their teams are said to have an ongoing rivalry, not much is shown about that though. The few times they had been shown together are rare. The first time they been shown passing each other in the GOTT but with no reaction on Tweedledum's part. On of the other example was as Alv and Dvergr came to help Tweedledum and Tweedledee by absorbing a bomb, Tweedledum wasn't exactly shown pleased with it but that also could because he didn't like the fact that he and his sister needed help. The other time they have been shown in the same area was during the battle against Alv and the Deucalion, were they didn't talk at all, but Tweedledum did join the fight against Alv with his sister.
Like with Alv, not much is shown about Tweedledum's and Dvergr's relationship. With both can be because of Dvergr's quite personality and the fact that Tweedledum isn't seen having much interaction with most of the other E.S members on screen.
While they aren't shown to interact much with each other on screen, they still are on speaking terms and have at least a good co-worker relationship.
Like with A-ou they aren't shown to interact with each other much on screen but are also on speaking terms and have at least a good co-worker relationship.
There aren't shown any interaction between the two on screen. Through it's most likely that they are on speaking terms and have a good co-worker relationship.
Like with his partner Dextera, there aren't any interaction shown between Tweedledum and him on screen. They still most likely are on speaking terms and have a good co-worker relationship.
As Cesario speaks as good as never and if he does, he does it in whispers to Viola, and as they aren't shown together much, there isn't much shown off their relationship. Still, it's most likely that they are on speaking terms and have at least a good co-worker relationship, like most of the E.S members.
Like with most of the E.S members, they aren't shown to have many interactions on screen. But mostly likely they are on speaking terms and have at least a good co-worker relationship.
During Kiddy Grade, there aren't much interaction between those two either. In Kiddy Girl-and through as Mercredi became Hiver and the director of the GTO and as such the boss of Tweedledum, they are on speaking terms and Tweedledum at last respect her as his boss.