Help With Sims 3

I am currently experiencing a really odd glitch and I was wondering if someone could help me rectify this;

I was playing with a household when one of my other households had a baby during this time, problem is it is as if the baby is there indicated through the green diamond thing but the baby is invisible and doesn't show up on the family tree either,

how can I make the baby become visible instead of it being blank?? help!