In 'Time Enough....' go back to the part where he meets his mother...... also, in the same book when Laz was on the prairie and he speaks of young girls (his daughter) growing up and etc. etc..... his later books definitely bordering on that topic in some fashion or another...it's why I got turned off to them in the end.
This is why I like his so-called "juvenile fiction" the best--Have Spacesuit, Will Travel, The Rolling Stones, Podkayne of Mars, Red Planet, Starman Jones, etc.. I remember reading Glory Road and waiting for the good parts that never came.