I would take that with a large pinch of salt, unless you can find some real proof !
I lived in Pontypridd (his birthplace, Treforest, is part of Pontypridd) from 1964 - 1970 and
almost everybody I met in that time either said that they were related to him (directly or by marriage) or that they "used to know him, when ... ", or went to school with him, or knew one of his ex-girlfriends, or ... or ... or ....
As a variation, if it wasn't themselves, it was the guy next door, a cousin, a friend etc, who .... see above