"He is the head of the house."
Translation:Ille est paterfamilias.
I don't see what is weird here.
"The gender is obvious by the predicate".
It doesn't mean that using the personal pronoun is wrong.
The version without the personal pronoun is more common, but it doesn't make the other one weird or wrong.
"Is" is not better than "ille", they are different. There are difference in the connotations. If someone can explain them in detail, it's not me for now.
I recommend you read the latin part of this word here: https://en.wiktionary.org/wiki/pater_familias#Latin
And also of "familia" here: https://en.wiktionary.org/wiki/familia#Latin
The word "paterfamilias" uses an old genitive (as) insted of "is".