Recently, the Lord convicted my heart that I wasn't spending enough time with my siblings. Don't get me wrong, I'm with them all the time, especially since we're homeschooled. However, I find that often, I spend too much time catering to them and less time considering them. Take Matthew for example: he's four years old and so tough on the outside. He loves guns and swords and his inside voice is louder than an average adult's football game voice. But, on the inside, he craves love, attention and direction. If he doesn't have something useful or instructive to do, he tends to act wild and get very loud. But, sit him down with a book; devote your time to him and he becomes as docile and loving as a sleepy puppy.
Next, let's consider Mirial. She's six years old and is the spitting image of myself. She is usually quite calm and lady-like (unless she's romping around with the boys) and acts mother to all younger (and occasionally older) than herself. Yet, she can get lonely sometimes and longs to be like the big girls (she loves to help clean and especially wash dishes). She deeply covets time with me, but I'm often too busy to do much but glance at her or get her a drink of water. Lately though, as I've taken the time every night to sit and read Elsie Dinsmore to her. This has been such a precious bonding time for us and I feel her heart growing closer to me every day.
The only reason I'm writing this is to encourage you to spend quality time and go out of your way to bless your siblings or your children. It pleases them and it gives glory to God because you naturally wouldn't want to do anything that doesn't involve personal gain.
Two more things important to your relationship with siblings (or children) are to praise them, then pray for them. Find their good qualities; if they do something exceptionally well, praise them, give them a smile and a hug or (even better) a special reward. You, especially as an older sibling can never understand what it does to a brother or a sister when you praise them. Don't tear them down with your words or actions, intentional or not. Go out of your way to encourage them. Try to praise them 10 times more than you correct them. It will make a world of difference! Believe me!
Pray for them, too. Praise them outwardly for their good qualities, pray inwardly for strength to conquer bad qualities. Never underestimate the power of prayer! Ask them what you can pray for them, if they need accountability as the Lord conquers their faults and shortcomings or for strength in times of temptation. This will change your life. It's always easy to see the bad in people and judge them as that, but it's hard to see them for who the Lord is making them to be. Applying praise and prayer will help tremendously in these areas and will give you the power to see others as not many people can.
Finally, ask God to open your eyes to see what He can do through you to bless your siblings and strengthen their relationship with you and Him. You'll be amazed at what He can accomplish in and through you as you seek to do His Will.