Music producer reckons the girls look great together
The pair were spotted kissing and cuddling at the Cannes Film Festival in France last month.
And Mark, 32, reckons they’re a great pairing.
‘My sister and Lindsay make a cute couple, don’t they?’ he tells the Sunday Mirror.
Neither Lindsay, 21, or Sam, 30, have confirmed they’re an item.
Earlier this week they were spotted partying with singer Lily Allen in LA.