What is it about him having a romantic relationship with one of your friends that bothers you? It can be hard to think a partner of your partner is worthy of him, but you already know her and like her...
Jealousy is something that needs to be worked through. Do a tag or word search here for tips and moral support.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
Mags, F, 60, poly-dating, loving and living with
miss pixi, F, 38
Punk, 42, M (dating since Oct 2015)
and a few more casual relationships