I wanted to check it out and it seems that it is true: old men are not dead men.
Adverse changes in semen quality with age have been reported but were slight (Nieschlag et al., 1982; Schwartz et al., 1983; Rolf et al., 1996). Neither sperm function in vitro (Haidl et al., 1996), nor the ability to fertilize donated oocytes (Gallardo et al., 1996) declined with age.Charlie Chaplin- fathered 8 children with Oona O'Neil, the youngest born when he was 74 (pic)
Anthony Quinn- fathered two children with his secretary (whom he later married) when he was 78 and 81
Saul Bellow- his youngest child was born when he was 85
Strom Thurmond- all four of his children were born when he was well over 60, the last when he was in his seventies
Clint Eastwood- his youngest child was born when he was in his late 60s
James Doohan ("Scotty" from STAR TREK) married a teenager when he was in his mid-fifties and had two sons, then had a daughter with her when he was 80 and his wife was in her 40s.