Micah Meggs, 15, was fatally struck while riding an electric bike on May 4 in Franklin County, Virginia, state police said at the time.
Olivia, 25, is married to Ethan Plath, the eldest of nine children who star on TLC reality show about their large family, "Welcome to Plathville."
In a tribute posted to Instagram on May 20, Plath explains how her parents barred her from seeing her brother in recent years due to her choosing a non-religious lifestyle, different from theirs.
"I can’t stop thinking about all of the memories we never got to make and how I missed out on the last few years of his life," she writes. "When growing up in a large family, the older kids often become like parents to the younger kids. Micah was my baby; I was 9 when he was born and I remember that day like yesterday."
Plath says she toilet-trained him, taught him to read, and carried him around like he was her own.
"Micah suffered his entire life from Cerebral Palsy caused by a Brachial Plexus injury during his birth which made it difficult for him to do the things he enjoyed," she said. "In lieu of flowers my family is requesting that those who are so inclined to donate to the Brachial Plexus foundation. Donations can be made at ubpn.org.
"Micah was only 15 and died in a tragic accident. Life isn’t promised; hug your loved ones a little tighter today."
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