Was Gilgit-Baltistan historically a part of Kashmir? Are the people of Gilgit-Baltistan and Kashmir related?

Lalitaditya of Kalhana's Rājatarangini

Lalitaditya Muktapīda, the greatest ruler of the Karkota Naga Dynasty, is said to have fought and conquered the Darads (Dards), Bhauttas (Tibetans), Some Central Asian peoples, and the rulers of Kānyakubja (Kannauj). This means that Lalitaditya's short lived empire spanned Gilgit-Baltistan, Central Asia, Ladakh, Punjab and modern-day Uttar Pradesh and vicinity. 

Sultan Sikandar Shah Miri 

This Sultan of the Shah Miri Dynasty, had controlled the areas of Gilgit-Baltistan, Ladakh, as well as parts of Khyber Pakhtunkhwa including Attock Khurd. After his death, these areas were lost under the reign of his brother.

Sultan Zain-ul-Ābidīn Bəd̥śah Shah Miri

Zain-ul-Ābidīn, the son of Sikandar, was a great Sultan Indeed. He promoted literacy and craft, and was a secular Sultan. He stabilised the rebellious areas of Gilgit-Baltistan and Ladakh, and reoccupied Attock Khurd. 

The Dogra Rule 

While Gilgit-Baltistan itself was independent, it's independence was much smaller than that of a Princely State. It came under the suzerainty of the Princely State of Jammu and Kashmir. Moreover, before Lord Curzon took over it, Chitral too, was under the suzerainty of Kashmir. 

Similarities between Gilgitis (Shinas), Kargilis (Drasi Shinas and Brokpas), Guresis (Guresi Shinas), Kashmiris, Kohistanis, Khos and Kalasha

The majority of these people, who are ethnolinguistically Dardic people  are adherents of Islam. Linguistically, they speak related languages. While it would require a very large space to write down their linguistic similarities, here are some examples-

Drasi Shina - /ʈʰuːl/, Kashmiri - /ʈʰuːl/

Khowar - /aowa/, Kalasha-mun - /a/

Drasi Shina - /be/ "we", Kashmiri - /bɨ/ "I", Indus Kohistani - /bé/ "we".