Why do i LOVE my baby sister so much?

i'm 18 and my Baby sister is 10 months old. shes adorable i love her i spend every second with her. i can't explain my love for her shes so cute. i spoil her more than my mom (and my mom spoils her) i work for Seventeen so i make a good amount of money... i don't know why but i always spend it on my sister. i have bought her Uggs, a cute little hoodie and pants juicy couture idk it just looked cute and i bought her does short jumpsuit and more uggs and i went into gucci for some sun glasses (with my sister of course) and i stopped in the baby section and i bought her some cloths (yes gucci has cloths for babys and so does juicy couture). i also enter her in beauty pageants she has done 2 so far my mom did the shopping i did the make up and the training she has done modeling for Childrens place. i love ebtering her in does. I always take her shopping and out with me i love taking her to the park and she loves shopping so i do it very often why do i love her so much?? i would kill myself for her