No. Sons-in-law in this instance refers to the men to whom his daughters were betrothed. By the standards of the day, even though they had not consumated the marriage, they were legally married, and would have to get a divorce (which is what Joseph planned to quietly do when he found out Mary was pregnant) in order to end the betrothal.
In reply to <p>Just to answer the bit by Patrick
No. Sons-in-law in this instance refers to the men to whom his daughters were betrothed. By the standards of the day, even though they had not consumated the marriage, they were legally married, and would have to get a divorce (which is what Joseph planned to quietly do when he found out Mary was pregnant) in order to end the betrothal.