Final answer:
After Guru Amardas, the lineage of Sikh Gurus continued primarily through his family, with Guru Ramdas, Guru Arjan Dev, Guru Hargobind, Guru Har Rai, and Guru Har Krishan all being directly related, either as sons or grandsons.
Step-by-step explanation:
The inter-family relationships of the Gurus after Guru Amardas are of historical significance in the context of Sikhism. Guru Amardas, the third of the ten Sikh Gurus, was succeeded by his son-in-law Guru Ramdas. Guru Ramdas was married to Bibi Bhani, the daughter of Guru Amardas. Their son, Guru Arjan Dev, became the fifth Sikh Guru. Guru Arjan Dev was succeeded by his son, Guru Hargobind, indicating a hereditary succession within the same family. The legacy further continued with Guru Hargobind's grandson, Guru Har Rai, and great-grandson, Guru Har Krishan. The eighth and the ninth Gurus were not direct descendants but were related to the previous Gurus through lineage or spiritual succession. The concept of Guruship then evolved, leading to the installment of the Sikh scripture, Guru Granth Sahib, as the final eternal Guru by Guru Gobind Singh, the tenth Guru.