HKFA lists them separately and I can't find any aka designation.
I'm guessing it's more likely they share the same family generation name.
So, they could possibly be siblings, or cousins.
Some examples:
http://www.geocities.com/Tokyo/3919/generations.html
Notice also HKFA's listing for Happy Together (1997)
Prop master: Tam Wing-Cheong, Asst prop master: Tam Wing-Hung
é