The nikkah is the most important hour of the wedding, and usually the quietest. It asks for clothes that are formal without being loud: the room should remember the occasion, not the outfit.
For the groom
A sherwani in tone-on-tone jamawar, ivory or a deep black, made to measure over three fittings. Allow ten weeks. Keep embellishment to the collar, and let the cloth do the rest. Pair it with a plain churidar and quiet leather shoes.
For the family
A karandi kurta with a raw silk waistcoat is the most elegant answer for a brother or father. Choose a waistcoat a shade darker than the kurta, with self-covered buttons. Nothing in the pocket, or a single folded square in white.
The groom should be the best-dressed man in the room, by a little.
For the guest
A plain kurta in a good cloth, or a dark suit with a white shirt and no tie for an evening nikkah. Avoid ivory, which belongs to the groom, and anything that catches the light.