OPOL - which languages does your DCs speak together?

[StoneBaby]

I'm French and DH English and we live in the UK. DS has been raised as OPOL and is fine with it and has no issues from switching languages depending on whom he speaks to.
Soon, a new DC will be born and We will do OPOL again.

However I wonder which language DS should speak to his sibbling? English as it is the majority language or a mix of French and English?

Thanks for your advices

DD1 spoke my language to the baby as she thought it was the only language the baby understood. So unless your DH is going to take sole care of the new baby, I suspect your DS will speak only french (like you!) to the baby.
At least at the beginning, when they both grow older I suspect only english will be spoken unless you move to france.

My two eldest speak French to each other (we live in France - French DH) and English to me. There is a huge age gap between them and our youngest (15 and 11yrs). She speaks English to everyone but DH.

So we have very interesting conversations between the three children who change languages depending on which sibling they are talking to.