I can tell you that it's not uncommon for some individuals to struggle with maturity or exhibit delayed development of certain social and emotional skills. There can be various reasons for this, such as personality traits, life experiences, mental health issues, or even certain developmental disorders.
If you're dealing with a situation where you have an adult sibling who seems to struggle with maturity, it can be challenging and might have an impact on your relationship with them. It's essential to approach such situations with empathy and understanding. Encouraging them to seek professional help, if appropriate, or engaging in open and honest communication can be beneficial.
Remember that everyone's journey is unique, and people may grow and mature at their own pace. It's essential to be patient and supportive while offering help when needed.