Where exactly is that requirement in the Old Testament that Jesus must assign responsibility for the care of his mother to his siblings and not to someone else?
Honoring your parents, according to Jewish tradition, included caring for them when they were dependent the way they cared for you when you were dependent and not placing responsibility for them on anyone not their child.
Anyone who wants to find more details can easily find them and anyone who prefers their own preconceptions is free to wallow in those preconceptions. Mox Nix.