You are kind to consider SD's sister.

You are a KIND soul. While the other child is not your concern, you are thinking about her. I love your idea of crafts....or other gifts that "need" two people. I don't feel you need to send a separate gift for the other child....but something YOUR SD could technically "share" her gift would be a great idea.  Gosh, I just LOVE your heart!!! 

 While I was shunned from being a grandparent to DHs grandchildren, I always encourage him to include gift giving to the two grand-SKs in his world. (Two of DHs sons are with women who had a child prior to meeting them.) Does it hurt?? Yeah...I'm not going to lie. But young children are innocent.

I stongly believe that God (or the universe, whatever your belief system may be) honors when we do good to those who we really don't need to good towards. You may never see the reward from that child or even your SD....but goodness will come your way. 

Best to you.

Great ideas! 

Do not try to mitigate potential issues at BM's.  SD's BM spawned half sib is not a factor in your family, in the CO that govern's your blended family life and denying your own family members due to "them" solves nothing.

My SS-32 is an only in our family but the eldest of 4 all out of wedlock Spermidiot spawned half sibs by three different baby mamas in the SpermClan.  Our situation was far more simple than yours is as my DW had full physical and legal custody of SS from birth.  SS had a long distance visitation schedule in SpermLand.  7wks per year. 5wks summer, 1wlk winter, 1wk spring.  CS was a pittance though according to SpermGrandHag that $110/mo for a year then $133/mo for 9 years payed for new homes, new cars, nice clothes, vacations, excellent schools, etc... for SS. Things that could  not be provided for SS's three younger sibs because of the pittance paid in CS.  When SS was 11, 9 years after we married, my DW filed for a CS review which kicked CS up to $785/mo.  SpermIdiot appealed and it was lowered to $365/mo two years later.  Even with that notable increase in CS, it was not enough to deny SS's sibs a thing but the toxic SpermGrandHag spun that web and still would be spinning that web if SS had not written them all off due to their toxic manipulation about 10yrs ago.

They tried to leverage guilt against SS to try to get my DW to drop CS.  Nope.  SS would never have to hearn that they did not give enough of a crap about him that they would not support him.  The quality of life his younger sibs lived was the responsibility of the SpermClan and the other two baby mamas. It was not on us.  SS did not have to live the life his sibs were raised with.

Meanwhile back at the ranch and a decade and half later, our son (m former SS who asked me to adopt him when he was 22) is a man of character, honor, and standing in his life, profession, and community.  SpermIdiot spawn #2 is on the dole, #3 is in prison, #4 is not far behind the inmate.

You cannot fix the shallow and polluted end of your SKid's gene pool. Don't waste yourself and punish your family by trying.  Focus on the things that you nave influence over. 

We never had the Christmas equity thing to deal with.  The SpermClan belongs to a fringe Christian cult that does not recognize or celebrate Christmas so Dec 25th was always my DW's in the CO.  In alternating years Winter visitation went from school end until Dec 24th and the next year from Dec 26th until school start. Travel in both directions was on their time .  So we did not have SS's half sibs to worry about when it came to Christmas gifts.  It was just not a consideration during the holidays.

We did offer to assume guardianship/custody of SS's three younger half sibs during a phase when the SpermClan claimed severe financial strain/hardship and claimed to not be able to afford SS's visitation travel to get him to them.  They made no office attempt to amend or end CS. They just used it as a major guilt campaign against SS. So we offered to assume care and custody of  his sibs.  You would have thought we had called them every name on the planet.  We knew what their response would be but we wanted to be sure to show SS that we heard his concerns and were willing and able to support his younger sibs.  He  (SS) remembers the call DW made to SpermGrandHag making the offer to take SS's sibs even 20 years later.  When the Hag blew her top SS was baffled.

My Dear Girl,

Once again, you remind me why I consider you to be the best, most thoughtful and proactive SM on this site. Your Christmas ideas for your SD, with the intention of including her older sister, warmed this bruised heart that took a beating on my birthday, 5th of November. Yup, you’ve proven (once again, Hon!) that there are still good people in the world; you renew my faith in human nature. ♥️

Kids are kids. They don't fully understand the The dynamics of life and family groups.  Be kind to SD sister.  Easier to be kind then unkind. 

Good ideas. I actually think it might be ok to send small gift for SD too. But crafts for two are awesome too 

When is your next visitation after Christmas? New Years? MLK weekend? To avoid potential issues, you can always 'celebrate' before or after the actual holiday. 

I see your good intentions with SDs sister. However, she might be feeling some type of way with the newborn... having a gift JUST for her might go a long way with SD. I agree that it is thoughtful to think of the other kids.