Change of LLC ownership

LLCs are regulated by state law, so you have to check the laws of your state.  The only federal issue I can tell you about is that when an LLC changes ownership (adds or removes a partner) it needs a new EIN.

https://www.irs.gov/businesses/small-businesses-self-employed/apply-for-an-employer-identification-number-ein-online

I have a 2 member LLC and they have transferred their ownership to two other individuals.

May have this wrong because of the language but if one of the 2 members transferred their ownership to two others then the LLC probably doesn't need a new EIN. 

it would seem that for federal purposes a partnership return need to be filed eaxh year. 

under current law there is no termination of the partnership for federal purposes

see this link we're post TCJA

https://www.irs.gov/newsroom/questions-and-answers-about-technical-terminations-internal-revenue-code-irc-sec-708 

the transfer if partnership interest may result in tax consequences for both the terminating members and new members

section 751 may affect the terminating partners