BRILLIANT!
The reference to Robert Lehar and Cicily Jobe popped up several times during my searches and I, ahem, discounted it. Oh, the shame! I must remember to think outside the ancestral box.
I’m certain you’re right because I’ve found another Cecily/Cecilia, daughter of Robert and Cicily’s son Thomas and his wife Elizabeth Teague. Right now, Robert and Cicily’s line looks look this:
Robert Leaha bp 15 Oct 1637 Paul, m. Cicily Jobe 23 Sep 1664 St. Ives
• Ralph Leaha bp 27 Mar 1665 Paul, m. Rebecka Unknown 22 Dec 1688 Paul, buried 07 Nov 1711 Paul
Children: Edward 1689, twin of Andrew 1689, Rebecka 1693, Robert 1696, Margaret 1698, Ralph 1701, Nicholas 1705
• Andrew Leaha bp 09 Mar 1666 Paul, m. Joan Tonkin 01 Dec 1712 Paul, bd 27 Dec 1699 Paul
• Thomas Leaha bp 10 Apr 1670 Paul m. Elizabeth Teage 29 Apr 1695 Paul
Chn: Elizabeth 1698, Thomas 1701-1702, Thomas, 1703, Cecily bp 29 Jun 1707 Paul, m. John Bremble 20 Feb 1741 Paul
• Eleizabeth Leaha bp 19 Jan 1672 Paul, d. BEF 1677 Paul
• Eleizabeth Leaha bp 01 Jul 1677 Paul
• Ann Leaha bp 19 May 1684 Paul m. John Cotton 23 Oct 1714 Paul
Chn: Catherine 1715, Ann 1716, Richard 1718-1720, John 1720, Margaret 1723, Rebecka 1725, Elizabeth 1730
I haven’t yet found a marriage for Elizabeth Leaha 1677, children for Andrew Leaha 1666 or parents for their mother Cicily Jobe.
As for the importance of the forename Andrew, it eludes me. My tree currently shows four of them but none as a patriarch. Instead I have an ever-growing number of Rebeckas. And Ralphs.
• Leaha, Andrew 1 1666-1699 son of Robert and Cicely
• Leah, Andrew 2 1689 son of Ralph and Rebecka
• Leah, Andrew 3 1726-1780 son of Robert and the elusive Ann Carveth
• Leah, Andrew 4 1767-1775 son of James and Elizabeth Davie
Earlier today, I revisited the Paul PR films and located the original 1688 marriage record for Ralph/Rafe Leaha and Rebecka Unknown, which was blessedly clear. He was recorded as Ralph Leha; her maiden name was left out. Since then I’ve traveled down some strange paths that are definitely outside the ancestral box. Using the Cornwall OPC site only, I tried running some searches for Rebecka without a surname, using the names of her kids as potential parents. I didn’t get a single hit from Paul but up popped an Andrew:
• Voysey, Rebecka bp 7 Sept 1665 St. Mellion daughter of Mr. Andrew and Rebecka
That “Mr. Andrew” is interesting. He may have been a gent, in which case I doubt he belongs on my family tree. I found two other contenders:
• Gummow, Rebeckah bp 23 Jan 1664 Newlyn E daughter of William and Margarett
• Rule, Rebecka bp 3 Feb 1666 Cambourne daughter of Robarte
Changing the spelling to “Rebecca” resulted in a confusing number of possibilities. The most interesting record contains two hits, one of which is Andrew as a surname. Hadn’t thought of that possibility before! It’s worth some research.

• Andrew, Rebecca bp 10 Mar 1667 St. Germans daughter of Wm and Margaret
Alas, she may have married a Thomas Gill in Liskeard in 1688. Short of running down each and every one of these Rebecka/Rebeccas to see if they have marriages on record that actually include their surnames, I have no idea where to go with this. Methinks it might be an exercise in frustration. Perhaps I’ll stick it back in the box!
Backing up two generations, I took a better look at Rafe Leaha and Elezabeth Unknown today. The film of their marriage record shows their names clearly but with no bridal surname included. They married 2 Oct 1636 in Paul and produced at least three children:
• Roabart Leaha bp 15 Oct 1637 Paul m. Cicily Jobe 23 Sep 1664 St. Ives
• Ane Leaha bp 14 Aug 1641 Paul (haven’t found a marriage yet)
• Ralph Leaha bp 11 Aug 1645 Paul, bd 14 Dec 1645 Paul
I tried to find a baptismal record for Rafe and, interestingly enough, found I could go in two directions -- with both leading to the same John Leye in Bodmin. First I found:
• Lea, Rafe bp 18 Apr 1579 Bodmin son of John
• Leye, John bp 10 Apr 1561 Bodmin son of John
I doubt Rafe was 57 when married in 1636. It appears I have a generation gap. Alternatively I found:
• Ley, Ralph bp 18 Jun 1617 St. Minver, son of Ralph
• Lay, Ralfe bp 12 Apr 1587 St. Minver, son of John
• Leye, John bp 10 Apr 1561 Bodmin, son of John
Good grief, I’ve seen that last guy before!

These were cursory searches; evidently I have some digging to do.
I appear to have written a treatise on Leahs. Tomorrow I shall return to the Ann Carveth fray and investigate your Madron/Penzance lead. Many thanks for your interest and help!