When soap kids are SORAS'd, miraculously somehow adults stay frozen in their current age, until they hit Doug and Julie age. Then they become the sage elders of the show.
In 1989, Scotty Banning was in his 20's, which would've made his dad David in his 40's, which would've put his mother Julie in her 60's, which would've put her mother Addie (had she lived) in her 80's, which would've put Alice over 100. So by the time Alice died in 2012, she'd have been over 120, thanks to her grandkids, great-grandkids and great-great-grandkids being SORAS'd.
Everybody around Joy knew the circumstances of her conception and birth, so it would've been hard to keep it quiet that she literally saved her sister's life with a bone marrow transplant.