We ask Allah to bless your marriage, Ameen.
In general tattoos are haram for the purpose of beautification.
The Prophet (peace and blessings of Allaah be upon him) cursed the one who does tattoos and the one for whom that is done. In al-Saheehayn it is narrated that ‘Abd-Allaah ibn Mas’ood (may Allaah be pleased with him) said: “May Allaah curse the women who do tattoos and those for whom tattoos are done, those who pluck their eyebrows and those who file their teeth for the purpose of beautification and alter the creation of Allaah.” (al-Bukhaari, al-Libaas, 5587; Muslim, al-Libaas, 5538)
But one can say, they aren't doing it for that purpose and want evidence suggesting tattoos are allowed as long as they are not for the purpose mentioned in the hadith. Then, because I'm not qualified to answer that, I would ask, Praise be to Allah
, but what can represent life long unity better than the love and mercy Allah put in the hearts of spouses for each other?
"And among His Signs is that He created for you mates from among yourselves, that you may dwell in tranquility with them, and He put love and mercy between your hearts. Verily in that are Signs for those who reflect." [Sûrah Rûm: 21]
Everything will but perish. But it is what spouses behold in their hearts and actions.. love, compassion, understanding and good treatment of each other
that is a true representation of unity in their marriage. If your hearts are embellished with what Allah likes then inshaAllah you already have the best symbol of unity two people can hope for. Just keep the emblems of unity in your hearts polished and shiny for the sake of Allah, and inshaAllah with Allah's Mercy and blessings, He will unite you forever, in Allah's Paradise in the Here-after. Ameen :)