I don't see any need to denigrate the weight or general character of the accused, in order to think of them as suspects in this case -- I don't see the twins' weight as being an issue at all in their potential involvement (or uninvolvment) in this homicide, nor do I think they're in general horrible people -- I don't have facts to lead me that way and nor do I think they are at all relevant to the case at hand. Nor do I think race is an issue at all in any of the findings. I can't see that anywhere.
What I do think is that if MY ex's girlfriend (now wife, and a truly heinous specimen - which is a fact, not *wholly* a value judgement, heh) was in charge of MY child and she was so gravely injured, and I could get no clear answers as to what happened, and I perceived untruths... and possibly got mistaken medical hints re deliberate harm, and was told she'd likely die.. well. I cannot for sure say where my rage would take me (nor that of several other family members who love her). That's just being 100% honest. My foaming dislike of the woman might be fuel to that fire, but I'd be after blood.. I would only hope, in a metaphorical sense.
If the defendants in this case truly are guilty of a murder - well, I can see why, without thinking for a moment it's a right and just course of action (as it clearly is not).
If we're talking how people can overpower people of disparate height/weight to themselves, it's done all the time. Allll the tiiime. Happens every day, kids kill their parents, wives kill their husbands, fat people kill fit people -- height, weight and relative fitness is absolutely no indicator as to whether a person CAN kill another person or not.
Especially where the victim had several head injuries.
^ All of this is "just sayin".