Objectives: To establish an analytical method for half sibling testing involving common three relatives' participation.
Methods: Based on the half sibling testing scenarios with the known biological mother, grandfather or uncle, and two unidentified controversial half siblings participating, two opposing hypotheses were set. Lineage reconstruction according to Mendel's law of heredity was carried out, and the calculation formula of the half sibling kinship index was derived. Verification of actual cases was carried out and the results were compared with duo half sibling testing.
Results: In the scenarios of the known biological mother, grandfather and uncle participating in half sibling testing, the kinship calculation formulae of 54, 91 and 99 genotype combinations for kinship index calculation were deduced respectively. The actual cases showed higher kinship indexes in trio half sibling testing compared with duo half sibling testing.
Conclusions: It is beneficial to obtain more genetic information for family reconstruction and improvement of the strength of genetic evidence for half sibling testing by adding known relatives.
目的: 建立常见的三个体参与进行半同胞关系鉴定的分析方法。方法: 针对已知关系的母亲、爷爷或叔叔和两个有争议的半同胞参与的鉴定场景，分别设定两个对立假设，按照孟德尔遗传定律进行家系重建，推导半同胞亲缘关系指数计算公式。通过实际案件进行验证，并与两个体配对半同胞关系鉴定比较。结果: 在母亲、爷爷和叔叔分别参与的三个体半同胞鉴定场景，分别推算得到54、91及99种基因型组合的亲缘关系指数计算公式。实际案例分析结果显示，与两个体配对半同胞鉴定相比，三个体参与半同胞鉴定的亲缘关系指数均增大。结论: 增加已知亲属参与半同胞关系鉴定有利于获得更多的遗传信息进行家系重建，提高半同胞关系鉴定的遗传证据强度。.
Keywords: family reconstruction; forensic genetics; kinship; kinship index; trio half sibling testing.