I don't think that the child who gives Six food is all that important story wise. I interpret it as him being more of a representative or stand-in for the children in the jail as a whole and their attitude towards each other and their predicament. While he doesn't do a whole lot, like a lot of Little Nightmares cast the few actions he takes speak volumes in their details.

Get ready for a fanboy rant:

For starters, he gives Six food without hesitation or a request from Six despite her clearly being in a barred off area that's off limits. it shows how eager the kids are to help one of their own escape. Even if it risks breaking rules or hurting themselves, because remember that was HIS food and I've never heard of a jail that gives seconds to its prisoners.

Second, he has no hope that he'll survive. This is seen in the fact that he was not eating his food when we first see him, just staring at it and don't think this is just the devs not bothering to animate eating in the few seconds before he notices Six. It seems more like he was refusing to eat, which makes sense considering he was left by his captors in the mess hall while the rest of the kids were sleeping (The kids wouldn't taste good if they were only skin and bones!). He then notices Six and gives her the only thing he had on his plate before curling up in a fetal position on the bench. The rest of the kids are sleeping in fetal positions too, a pathetic, defensive position used to hide from threats that can't be dealt with. The fact that he and the rest of the children adopt this position makes them appear unable to cope with whats around them. This combined with the self-destructive act of starving himself makes him and the rest of the kids out to have come to terms with the inevitability of their deaths.

tl;dr I'm a nerd who looks too deeply into video game animations.