Ten years from now, the elder child will be 20+10 = <<10+20=30>>30 years old.
If the elder child is 20 years old now, the second born is 20-5 = <<20-5=15>>15 years old, 5 years younger than the firstborn.
The second-born will be 15+10 = 25 years old ten years from now.
The total age of the first and second-born 10 years from now will be 25+30 = <<25+30=55>>55
The third-born who is five years younger than the second born is 15-5 = <<15-5=10>>10 years old.
The third sibling's age ten years from now will be 10+10 = <<10+10=20>>20 years old.
The total age of the three siblings ten years from now will be 55+20 = <<55+20=75>>75 years.
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