ds wants to use both surnames (not just dad's)

[Pringlesaremoreish]

Hi all, 16 year old ds wants to use both mine and my husband's surnames (and not just his dad's). He's only got his dad's on his birth cert and I wondered whether anyone else has done this? Is it as simple as him just using both names, or do we need to get it legally changed? TIA

He’s 16, so it’s just a case of deed poll to do it legally.

Regarding legal vs known as.
He can be known as just about everywhere just by adopting the name including medical records etc.
Legally he would have to change it to have it on driving license and passport etc.

Thanks JoshLymanIsHotterThanSam, much appreciated.