chinless wonder

Etymology
The term is derived from the characteristic recessive chin of some aristocrats, popularly thought to be caused by inbreeding and associated with limited intelligence, and from the idea of a robust chin being an indication of masculinity. The use of 'wonder' is ironic.

Noun

 * 1)  An ineffectual upper-class man, typically dim-witted and of a weak or indecisive character, frequently one who gained his position through nepotism or social connections.

Synonyms

 * twit