Who files the taxes?

[Darren Jordan]

Hello BP,

If anyone can answer the question to this scenario I'd appreciate it! I don't believe it is too complicated but scoured the web for awhile with no luck answering my question.

The scenario:

A family member (father) buys a 'secondary residence', which includes a mortgage loan under his name to purchase the property but also puts his son's name on the deed along with his own name (father).

The son moves into this property and lives there for 5+ years, he assumes all responsibilities (pays mortgage, property taxes, insurance, etc.) and also files the mortgage interest every year with his taxes.

In the event the property is sold. Who reports the sale of the house to the IRS? Can the son do it? 

What it really boils down too, can the family avoid the capital gains tax on the property at time of sale since it was originally established as a 'secondary residence' but really treated as a 'primary residence' for the son over the last 5+ years.

Thanks in advance!!!