When writing a wedding card for a family member, its important to strike a balance between being personal and appropriate. Here are some ideas to get you started:

• "Congratulations on your marriage and welcome to the family!"
• "Were so happy to have gained another sister/cousin/aunt. Best wishes to you both!"
• "Youve felt like part of the family from the start. Were so glad its now official!"
• "Our family has gained a wonderful new member. Were so happy to share in your love and special day."
• "Youre now a treasured branch on our beloved family tree and were forever grateful. Congratulations on your nuptials."

Remember to consider your relationship with the couple and choose a message that feels genuine and heartfelt. You can also add a personal touch by sharing a special memory or offering marriage advice. Above all, keep your message positive and celebratory, and end with a simple sentiment like "best wishes" or "congratulations!"