siblings of Sweetheart xx

half siblings maternal 3 half siblings paternal 4
  half siblings maternal (3)
  half siblings maternal (3)
  half siblings paternal (4)

half siblings maternal

horse Kingfisher xx (Thoroughbred, 1864, from Fisherman xx)

Kingfisher xx
gender-male
1864

Fisherman xx / Harkaway xx

broodmare The Fawn xx (Thoroughbred, 1865, from The Premier xx)

The Fawn xx
gender-female
1865

The Premier xx / Harkaway xx

horse Day and Martin xx (Thoroughbred, 1862, from Mr Martin xx)

Day and Martin xx
gender-male
1862

Mr Martin xx / Harkaway xx