USA 2016 1040 Schedule D question

[Art]

REc'd proceeds from a home sold in 2016. Home was deeded to 5 siblings in 1998. Each sib rec'vd $36729 from sale. We paid an estimated tax of over $5K in 3rd Qtr. After accumulating appreciation , sale less cost came to $18400. I think I add that amt to 1040 , line 13, with no form required. That increases our ordinary income. I thoughtr the max tax on this type of sale was/is 15%.. but I don't see where on 1040 that would be reflected. If I carry over from line 37b to line 38, the sale proceeds net appear to be included in ord income. HELP!