i know double barrel names are "cool" to have these days, ie: to honour both parents or sets of parents etc, but it doesnt scale beyond one persons choice to do it (unless you are nuts).
If it became the norm and Emile Smith-Rowe married Wright-Phillips sister, and they had a boy call Fred, Fred would be Fred Smith-Rowe Wright-Philips.
Then if Freds daughter (called Maria) married Reece-Moggs son, it would be Maria Smith-Rowe Wright-Phillips Reece-Mogg..........and so on and so on and so on.....
Which kinda says to me, that this double barrel stuff is nonsense beyond the initial "double barrelling", unless you want an entry in the Guinness Book of Records......