I've heard that when it comes to naming their first born sons, Japanese parents often use the kanji for "one", "一" like "一郎" for example, as their given names, and for second or third sons the kanji for two and three may be used respectively.
However, is it strange to come across names where " 一 " Is used in one's given name even if they aren't the first born son? I ask this because I'm reading a Japanese light novel where the character's name is 一温 and not much is known about his siblings but it seems as if he might have an older brother.