Anyway, what I did was brainwashed my gal before dear son was born, telling her her lil' bro loves to play with her and loves her alot. When dear son was out, I'd get my gal to help out, eg. take diaper/diaper cream/wipe butt for her lil' bro. When dear son needs me, I'll tell my gal to wait for awhile, her lil' bro needs attention. Then when he's asleep or what, then I'll play with my gal for awhile. Or I put both of them together to play, bonding time every 4pm for both of them.
Slowly take time.. dont be sad over yr inlaws' comments.