Where those girls twins and were they Larry's?

When Isabel left Larry for good in Paris because she didn't want to live a "normal" life, she ran off to marry Gray who was filled with money and could give Iz everything she wanted.

The next time we see her is when they're having a party and there are 2 little girls that belong to Isabel and Gray.

My question is, what's the timeline between Isabel leaving Larry and marrying Gray, and when the babies arrive and are they twins?

The reason I ask is I wonder if they are Larry's girls based on how they warmed up to him and the fact we never really see Gray close to the girls at all.