they're cousins. ice cube produced a good chunk of "I wish my brother George was here" which is Del's first album... and they have a funny interlude at the end of the album.
voice:"is that (dude) del your cousin?"
cube:"yeah man, he's my cousin. I be trying to get him to do some gangster shit, but he ain't with it man... i guess he one of those handkerchief-hat-wearing-motherfuckers. DOn't pay any attention to him man, he's kinda weird!"
i don't know if they've done anything together since... their styles aren't exactly compatible...