Invitation letter to parents-in law and brother in law

[apsingla]

Could anyone please suggest if

I should write a combined letter to my parents and my brother? or

My husband (main sponsor) should write an invitation letter to his parents-inlaw and brother in law.

I read in a thread that it makes sense if being a daughter i write a letter to parents.

Now is it OK to write separate letters one for parents and one for brother or just 1 combined letter?

thanks.

[peace]

one letter by you is fine if they are appearing together.

[apsingla]

thanks

Thanks a lot.