I’m sure they can… they do for other ‘weddings’… The New Testament does not mention gay marriages but it does mention fornication… Fornication, either hetero or homo, is still fornication… As far as the Established paper work that comes with ‘legal marriages’ are concerned, I don’t think Gentiles need to follow Jewish ‘marriage’ Laws.
If a Gentile has the desire to follow God more Lawfully, according to God’s Laws, then being indoctrinated into the Jewish life, through the baptism into Christ Jesus, who was Jewish, could help the Gentile receive The Law of God which was handed to Moses and then to The Sons of Jacob, more easily and conveniently.
If a Gentile is ‘baptized’ into The King of The Jews, the Gentile would become part Jew.
Where did baptism come from? The Jews or the Gentiles? I mean, don’t find it strange that Jesus Christ followed The ‘Sacrament’ of Baptism that God established through John the Baptist. Jesus Christ was only following what God desired.
Unto the Gentiles these commandments were given: Acts 15:13-29
"13And after they had held their peace, James answered, saying, Men and brethren, hearken unto me: 14Simeon hath declared how God at the first did visit the Gentiles, to take out of them a people for his name. 15And to this agree the words of the prophets; as it is written,
16After this I will return, and will build again the tabernacle of David, which is fallen down; and I will build again the ruins thereof, and I will set it up:
17That the residue of men might seek after the Lord, and all the Gentiles, upon whom my name is called, saith the Lord, who doeth all these things.
18Known unto God are all his works from the beginning of the world. 19Wherefore my sentence is, that we trouble not them, which from among the Gentiles are turned to God: 20But that we write unto them, that they abstain from pollutions of idols, and from fornication, and from things strangled, and from blood. 21For Moses of old time hath in every city them that preach him, being read in the synagogues every sabbath day.
The Letter to the Gentile Believers
22Then pleased it the apostles and elders, with the whole church, to send chosen men of their own company to Antioch with Paul and Barnabas; namely, Judas surnamed Barsabas, and Silas, chief men among the brethren: 23And they wrote letters by them after this manner; The apostles and elders and brethren send greeting unto the brethren which are of the Gentiles in Antioch and Syria and Cilicia: 24Forasmuch as we have heard, that certain which went out from us have troubled you with words, subverting your souls, saying, Ye must be circumcised, and keep the law: to whom we gave no such commandment:…