Welcome to our forum.
It sounds like you have some fears/trepidations about getting very emotionally involved with someone, if you are sexually involved as well. Certainly relationships like that can get complicated; you just have to decide if it's worth it.
Are DC and DI still married? What are their long-term plans? Does MP live in the same house with you? Do you have your own bedroom?
I hope we can be of some kind of help to you here on Polyamory.com.
Love means never having to say, "Put down that meat cleaver!"