Translation:He is old enough to be your father!
When you express purpose/ cause and effect with an infinitive you need to have "til å".
"Ibsen var for syk til å komme."- Ibsen was too sick to come. (Cause and effect/ purpose)
Han fortsatte å skrive til 1900- He continued to write until 1900. - (not cause and effect purpose, he wasn't continuing in order to write , his writing went with his continuing)
Does that make sense?