Howlett is married to Appleton's sister Natalie, and he had become close friends with Gallagher - the couples often holidayed together and the two musicians were photographed out on mammoth drinking sessions.
However, since Gallagher's split from Appleton, Howlett has barely spoken to his old pal because he feels he must remain loyal to his wife's sister.
Howlett tells Mojo magazine, "Me and LG, as a mate, we had plenty of laughs. Now I don't speak to him much. Basically I've got to look after my sister-in-law, know what I mean?"