Jupiter in 7th house is not considered good as written in Lal Kitab "These people should stay away from Saints and should not establish a temple at home" -These people are anyhow charitable by nature if Jupiter is in good dignity.

When they start doing work of Jupiter such as praying and taking interest in religious activities -They activate this Jupiter- Even by giving charity, they are continuously activating this Jupiter.

This person will anyhow do better in life than his father and guru due to this placement of Jupiter and people will remember him for his good deeds, This person will be like "Do not care" attitude even if someone does bad to him as his brain is somewhat different than normal people.

This House is 11th to 9th -Jupiter being the planet of expansion and giving out with a full heart- More this person gets involved with religion -He is always ready to help people even at his own personal cost.

A time comes in this person's Life at the age of 31 or 33 when due to him -His father and guru will always be benefited due to him and make a lot of money due to his hard work in these particular years, Might be possible will work with Guru so that he can make money.

So, When a person will get involved in religion to an extent- Sexual life will get affected badly- There are a lot of other factors such as a sign, aspects, nakshatras have to be considered but this is a basic over the line of the story that why Jupiter in 7th house will spoil a marriage.

As after marriage, only this Jupiter will get activated as You have activated 7th house in a chart so the person will become religious after marriage due to wife only.

The remedy is to make a balance in life between religion and married life, Also staying away from all religious people will help.