What is your source for this? The betrothal period of one year was PRECISELY for the reason of ensuring a woman was not carrying another man's child. It WAS custom. From http://en.wikipedia.org/wiki/Betrothal#Betrothal:
In Jewish weddings during Talmudic times (c.1st century BCE - 6th century CE), the two ceremonies of betrothal (erusin) and wedding usually took place up to a year apart; the bride lived with her parents until the actual marriage ceremony (nissuin), which would take place in a room or tent that the groom had set up for her. Since the Middle Ages the two ceremonies have taken place as a combined ceremony performed in public. The betrothal is now generally part of the Jewish wedding ceremony, accomplished when the groom gives the bride the ring or another object of at least nominal value.[5] As mentioned above, betrothal in Judaism is separate from engagement; breaking a betrothal requires a formal divorce, and violation of betrothal is considered adultery."
"After the marriage covenant had been established, the groom would leave the home of the bride and return to his father's house. There he would remain separate from his bride for a period of twelve months.7 This period of separation afforded the bride time to gather her trousseau and to prepare for married life.8 The groom occupied himself with the preparation of living accommodations in his father's house to which he could bring his bride." http://www.biblestudymanuals.net/jewish_marriage_customs.htm
Joseph, of course, knew the child was not his, but it took the angel in his dream to convince him why he should proceed with the marriage. As far as Joseph being an "old" man - that is NOT based upon anything but legend, myth, conjecture. He was obviously spry and strong enough to travel with a very pregnant Mary on a donkey the entire distance to Bethlehem, wasn't he?
I don't know why you accuse me of "laughing" at tradition. I certainly don't. As to Joseph being too old to father children, that is NOT a tradition in the true sense of the word. Besides, wasn't Abraham a hundred years old when Sarah conceived Isaac? And wasn't Jesus referred to many times as the "son of the carpenter"? Obviously, other people back then didn't think Joseph couldn't be his father. Poor arguments, JA.