Margaret,
Regarding Ruth’s middle name, her birth certificate doesn’t contain a middle name. She was just given the name Ruth. See:
https://civilrecords.irishgenealogy.ie/churchrecords/images/birth_returns/births_1868/03433/2260180.pdf
Sometimes people born without a middle name acquired one when they migrated to North America as middle names were definitely more common there. It wouldn’t be surprising if B did stand for Bruce. It was quite common to use a mother’s middle name in that way.
Thomas born 23.3.1866 wasn’t a twin. (That’s evident from his birth certificate. Twins have their time of birth recorded, and would normally be adjacent in the records). I can’t see a birth for William John. That suggests he was born before 1864. So possibly in 1862 as per the Holland family tree.
You enquire about the 1899 will, Edward Sinclair wasn’t the recipient. He was the executor. Presumably someone that William John Crowe felt he could trust. A neighbour evidently from his address. You would need to get a copy of the will to find out who the beneficiaries were.
I found a marriage for Jane Crowe to George Hull (also from Ballycollin) on 12.6.1891:
https://civilrecords.irishgenealogy.ie/churchrecords/images/marriage_returns/marriages_1891/10666/5886693.pdf
Here’s the family in 1901:
http://www.census.nationalarchives.ie/pages/1901/Antrim/Ballygomartin/Englishtown/988922/
And in 1911:
http://www.census.nationalarchives.ie/pages/1911/Down/Breda/Ballynavally/247700/
These might be two of George Hull senior’s children (both died intestate):
Hull, George of Mullaghglass Stoneyford Lisburn county Antrim quarry worker died 10 January 1963 at White Mountain Lisburn Administration Belfast 11 June to Sophia Hull the widow. Effects £204 8s.
Hull Richard of 96 Dunedin Park Belfast quarryman died 9 March 1947 at Upper Ballysillan Belfast Administration Belfast 29 July to Catherine Ann Hull the widow. Effects £141 2s. 4d.
In addition, I suspect George senior died 5.10.1963. He doesn’t appear to have left a will.
You can view all 3 of the above death certificates on-line on the GRONI site. https://geni.nidirect.gov.uk
George junior appears to have died in an accident at White Mountain quarry up above Belfast. He was the foreman and apparently fell into a 40 foot stone cleaning tower. He had gone to the top of the tower to switch off some electric powered plant. He didn’t return and was then found at the foot of the tower having apparently fallen in it and been smothered by stone. The death was reported in the Belfast Telegraph of 10th January 1963. The following days paper contained a family death notice, together with a sympathy message from his Orange Lodge in Stoneyford. He was buried in Ballinderry Middle graveyard. The Belfast Telegraph of 12th Jan 1963 contains sympathy notices which give details of some of his family: daughter & sister in law Eileen & Johnny Harbinson, Stoneyford; daughter and son in law Myrtle & Billy Heaney, 8 Templeton Park, Templepatrick; sister and brother in law Margaret & Frank Watson 3 James St, Lisburn; sister in law Cis, 53 Westmoreland St, Belfast.
You could possibly get a researcher to try and trace the people mentioned in the 1963 newspaper (or their descendants).
Researchers in the PRONI area: http://sgni.net
I hope this helps a little. (I am not connected to these families. I am a volunteer for Ireland Reaching Out who lives in Co. Antrim).