Look for his and hers gifts. From matching sports jerseys to coffee mugs, couple gifts are abundant in almost any outlet. If your sister and her husband are sports fans, consider ordering specialty jerseys with their first names or last name on the back of the jersey. This way when they attend games together they can represent their couple status. Towels are another popular his and hers gift as you can purchase matching towels with your family members' initials on them. The towels will dress up their bathroom and will help them tell their towels apart after use.

Give your brother-in-law and sister a gift that they can share and enjoy together. For example, if your favorite couple is a fan of barbeque, buy them an outdoor grill that they can use together. Include a gift basket of various marinades or barbeque sauces that they can use for their first grilling session. Gift cards are another great combination gift. Purchase a gift card to a restaurant that you know both parties enjoy. Treating them to dinner is another way to give them a gift that they can both enjoy together.

Rekindle old memories. Think back to when your sister and her husband were dating. Purchase a gift that will bring back memories from that time. For example, if they had a favorite weekend getaway story, try to recreate that weekend by making them reservations at the same places that they visited during that trip. You could also rekindle memories by creating a gift basket that has some of their mutually favorite items. This could include concert tickets or a copy of a movie that they went to and enjoyed together. Include some of their favorite treats. If their favorites vary a little, which is likely, make two baskets with similar items in each.

Purchase Mr. and Mrs. gifts. Married couple gifts can come in almost any style or object that you can imagine. Often these gifts are knickknacks that are useful around the house such as coasters or bathrobes. These also come in the form of wall hangings that sometimes commemorate the date that the marriage took place. Give your sister and her husband a gift that will remind them of their lifelong pact to each other every time they see it or use it.