The 1831 census of Drumachose lists 3 Steel households: Alexander, Jane & James. Here’s Alexander who had 2 households under his roof. There were a total of 6 people, 3 male and 3 female, all Presbyterians:
http://www.census.nationalarchives.ie/pages/1831/Londonderry/Kennaught/Drumachose/Carran/1/
The other 2 families were Presbyterian too. That’s indicative of Scottish origins, usually in the 1600s.
Birth & death registration didn’t start in Ireland till 1864. Presbyterian marriages were registered from 1845. Prior to those years you need to rely on church records. Not all churches have records for the 1700s and early 1800s and of those that do, they are often not on-line.
There are 4 Presbyterian churches in the area: Derramore, Drumachose, 1st Limavady & 2nd Limavady. Derramore has the earliest records but they only start in 1825. So it’s unlikely that you are going to find any record of the family’s baptisms or marriage as the records just don’t exist. Presbyterians rarely kept burial records so unless Mathew has a gravestone, he is likely to be hard to find too.
The townland where Alexander lived was Carran. He looks to have been a farmer as he is listed in the tithe applotment records for the townland in 1826:
http://www.irishgenealogyhub.com/derry/tithe-applotments/drumachose-parish.php
Griffiths Valuation for 1856 lists an Alexander Steele in Carran. He had plot 10 which was a 24 acre farm. That farm, today is on the Edenmore Road which is on the southern outskirts of Limavady. Some of the farmland has been built on with modern housing, and some remains in agricultural use. It’s hard to tell from Google Earth whether any original buildings are still standing. On balance I think they have gone but you would need to check that.
http://www.askaboutireland.ie/griffith-valuation/index.xml?action=nameSearch
This family farming in the townland in 1901:
http://www.census.nationalarchives.ie/pages/1901/Londonderry/Fruithill/Corran/1525493/
Both had left by the 1911 census.
Some mentions of Ralston in Lisdivin:
Firstly from the Abercorn estate papers:
https://cotyroneireland.com/estates/abercorn_donelong.html
Secondly a will:
In the Name of God Amen I NANCY McELHENNY of Lisdivin in the parish of Donagheady County of Tyrone being weak in body but of sound and perfect mind and memory Blessed be Almighty God for the same so make and publish this my last will and testament in manner and form following (that is to say) first I give and bequeath unto my son WILLIAM McELHENNY the sum of ₤180. I also give and bequeath unto my daughter MARGARET McELHENNY the sum of ₤180. I also give and bequeath unto my son JAMES McELHENNY the sum of ₤130. Exrs. first paying my daughter MARGARET the Bond debt JAMES owes her, then he to receive the remainder of the ₤130. I also give and bequeath unto my son JOHN McELHENNY now in America if alive the sum of ₤130 and if dead his share to my son WM. And my daughter MARGARET equally divided. I also give and bequeath unto my granddaughter MARTHA SMYTH the sum of ₤30 provided she behaves to the satisfaction of my Exrs. and if not the sum of 5 s. only. I also give and bequeath unto my daughter NANCY SMYTH and her five oldest children the sum of ₤50 to be equally divided amongst them the children not to receive theirs until the day of their marriage or Nancy’s death whichsoever may take place soonest. I also give and bequeath unto my son WM. and my daughter MARGARET all my household furniture equally divided. I hereby appoint my son WM. McELHENNYand my daughter MARGARET McELHENNY my sole Exrs. of this my last Will and Testament.
In witness whereof I have hereunto set my hand this 10th day of September 1825
NANCY McELHENNY [her mark], THS. RALSTONE, ROBERT ROLLESTON
Proved at London 22nd May 1827 before the Judge by the oaths of WILLIAM McELHINNY the son and MARGARET McELHINNEY otherwise McELHINNYspinster the Executors to whom admon. granted having first sworn by Commission duly to administer.
No Ralstons listed in Griffiths in 1858. They had evidently died out or left. The only church with any records for Donagheady in the 1700s is the Churhc of Ireland. Their records start in 1697. There’s a copy in PRONI in Belfast. Personal visit required to view them. There are 4 Presbyterian churches in the parish: 1stDonagheady, 2nd Donagheady, Donnemana & Magheramason. There is also a Reformed Presbyterian church at Bready. The earliest records are 2nd’s which start in 1838. The tithe records for that parish have been lost. So again you will struggle to find much on this family for the period you need.