Alliance Party's Naomi Long and SDLP MP Mark Durkan both revealed they were in favour of the equal marriage bill at the House of Commons on Tuesday evening.
Ms Long, who represents the East Belfast constituency, said, "As a Christian and a liberal, I believe that equality and religious freedom are fundamental to a democratic society and that both must be promoted and protected, a position which is reflected in our policy and also in the bill."
She explained that she was encouraged by the government proposals to support faith groups who do not agree to same sex marriage.
"It is also important in the context of religious freedom, that those faith groups who wish, in conscience, to marry same sex couples are able to do so without being prevented by the state, something which is also contained in the Bill," she added.
"My continued support for the progress of this legislation will depend on the robustness of the protections which are finally established during its passage through Parliament."
Alliance adopted a policy in favour of the extension of civil marriage to same-sex couples, provided that robust protections were put in place to protect religious freedom and practice.
Currently same sex couples can opt for civil partnership which offers the same legal rights and protections on issues such as inheritance, pensions, and child maintenance. However, supporters say gay relationships should be treated in exactly the same way as heterosexual ones.
But Ms Long voted against the Programme Motion, which sets out the timetable for the next stages of the bill, as she said she believes more time should be given to consider the issues raised.
The SDLP leader Alasdair McDonnell and the party's former chief, Margaret Ritchie did not vote.
Nine local MPs, including DUP members Gregory Campbell, Nigel Dodds, Sammy Wilson, Rev William McCrea and Ian Paisley voted against.
Independent MP Lady Sylvia Hermon joined the DUP MPs Jeffrey Donaldson, Jim Shannon, and David Simpson in opposing the bill.
Following six hours of debate, the rest of the house voted overwhelmingly in favour of the on the Marriage (Same Sex Couples) Bill, which Deputy Prime Minister Nick Clegg said it was a "landmark for equality".
"Marriage is about love and commitment, and it should no longer be denied to people just because they are gay," he commented.
Equality campaigners have welcomed the vote, which Equal Marriage NI chairperson, John O'Doherty described as a victory for decency.
"The tone of the debate in the House of Commons was overwhelmingly measured and respectful," he said.
What we saw in Westminster was a victory for equality and a victory for decency.
However Mr O'Doherty called for clarification over some terms of the bill, which will only apply to England and Wales.
"We do have concerns with the current version of the bill, particularly the provisions which mean that a couple legally married in England or Wales will have their relationship only recognised as a civil partnership in Northern Ireland," he explained.
"This would result in an untenable anomaly. As the bill enters committee stage we will seek to work closely with members of all parties and ensure that an amendment is introduced so that a couple married anywhere in the UK will be recognised as such everywhere in the UK."
For Prime Minister David Cameron, the bill split his party, with 136 Conservative MPs voting against equal marriage. He has been a driving force behind the cause of equal marriage rights, but 35 Tory representatives opted not to cast their vote, and just 127 revealed they are in favour of the same sex union.
However, Labour and the Liberal Democrat parties backed the bill in their majority.
The bill will now go forward to the House of Lords, where it is expected to face stiff opposition.