No, Near is not L's little brother.
Near, whose true identity is Nate River, is known as one of L's two successors, specifically the younger of the pair. Their relationship is professional, built on the premise of L training highly intelligent individuals to carry on his work.
Near was raised in Wammy's House, an orphanage established by Watari to cultivate gifted children. This unique institution serves as a breeding ground for brilliant minds, many of whom are groomed to potentially become the next L. Near's upbringing in this environment signifies a mentor-protégé dynamic with L, rather than a direct family connection.
Furthermore, Near has an older twin named Kerry, who was also raised within Wammy's House. This detail reinforces the concept of Wammy's House as a specialized educational facility for exceptional children, where individuals like Near are prepared for roles similar to L's, rather than a place where L's actual siblings would reside.
