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yes its possible however its not that common, if someone is sincere they embrace sikhi and take amrit first. And most strict sikh amritdhari daughters and their families do not want to marry to non-amritdhari sikh guys let alone a non-sikh.
One of the hukamnama''s (commandments) of Guru Gobind Singh Ji regarding the Khalsa is for not to give your daughter hand in marriage to a non-sikh. As Guru Ji knew most females tend to follow the male partners religion / lifestyle.
I think it is possible for a non-Sikh man to become a deeply religious Sikh if he converted to Sikhism for marriage especially if the bride’s devout Sikh parents demands that the couple live with them
Dear Amrit Singh, that's the good question you have asked? Even if the non-Sikh man is to embrace Sikhism for the sake of marriage and not for the love of Sikhi but it is almost assured that their kids would follow Sikhi as they have set a perfect example of utmost sincerity by following the Code of Conduct of Sikhi.before them.
Most of us lead a double standards when it comes to following Sikhism. We try to manipulate Sikhi to our own benefits as to what suits us. Ask any clean-shaven Sikh as to why he doesn't follow the Rehat, the prompt reply will come from him saying either he had to trim his outer identity because of the persecution he had to face in 1984 in India else he would say I am a Sikh at heart better than those who are Sabat Soorat Sikhs.
Similarly, when it comes to marriage those have fallen in love outside their faith will give n-number of excuses, the perfect example they will give you is, All the human race is One, we do ought to follow humanity irrespective of race, religion, and nationality, didn't our Gurus tell us this, didn't our Gurus tell us that, etc., etc.
So, all the discussion about what is correct or not correct in Sikhism depends on the Sikhs themselves. The fact is most of us listen and tend to follow their hearts and not brains.
My wife was an amritdhari before our marriage. I think it was a coincidence that I met her at Home depot or guru ji sent her to me to teach me about sikhi!
It's quiet funny that I had genuine love for sikhi and I also converted to marry her.