11:48 AM PT -- Matt Barnes has weighed in on the engagement ... saying he's happy for EVERYONE involved!
"I have two beautiful boys from my ex we are both focussing on co-parenting & providing the best atmosphere & childhood for them," Barnes said ... "They love him, so I love it.
"Despite not seeing eye to eye initially w Derek he & I are on the same page & communicate weekly about Isaiah and Carter."
"With that being said congrats on the engagement!"
Derek Fisher Proposes to Gloria Govan, She Said 'Yes!'