Sorting out the order of births in the Stanley family: a challenge!

I have become aware recently of a ridiculous claim by someone calling
himself "Prince David Howe-Stanley" to be the rightful monarch of the
Isle of Man. This claim is based on his apparent belief that the
Stanleys, Earls of Derby, who were granted the lordship of the island
by Henry IV in 1406, held it not by English but by Manx law, and that,
by some twisted misapprehension of Manx succession law, gender-blind
succession prevailed - i.e. the Lordship was inherited by the eldest
child regardless of gender. (In reality, it was inherited largely by
means of male primogeniture, with further confirmatory grants by the
British crown in cases of dispute.)

I would be interested in any comments or observations on this 'claim'.
In particular, I am struck with its apparent lack of internal logic.
The claimant alleges - without providing any evidence - that he
descends from Jane Stanley, daughter of George Stanley (d 1497),
himself eldest son of Thomas, Earl of Derby and King of Man (d 1504);
he alleges that Jane was George's eldest child.

Is this known to be the case?

In terms of consistency, I wonder whether george (d 1497) was the
eldest child of the eldest child etc of the original grantee of 1406,
Sir John Stanley. Is the birth order of the following known?

(A) the children of Sir John Stanley, died 1414, the grantee of 1406.
He was succeeded by his eldest son, John the younger, but the elder Sir
John also had two daughters - perhaps one of these would have been the
gender-blind heir?

(B) the children of Sir John Stanley the younger, died 1437. He was
succeeded by his eldest son, Thomas, but there were likewise two
daughters - was either of these older than Thomas? I note that Thomas
was knighted circa 1431 (according to Roskell) and fathered a son in
circa 1435, whereas his sister Isabel's marriage contract is dated 1422
(according to PROCAT)

(C) the children of Thomas, 1st Lord Stanley, died 1459. He was
succeeded by his eldest son, Thomas, afterwards 1st Earl of Derby.
There were three daughters, Margaret, Elizabeth and Catherine. *My
personal view is that this is probably the weakest link: was Thomas,
1st Earl of Derby, younger than any of his sisters?*

mjcar...

Here is where I think a chink may be exploited:

Thomas, 1st Lord Stanley's daughter Elizabeth married Sir Richard
Molyneux (d 1459). Their eldest son (there was also a daughter
Margaret, wife of Sir William Bulkeley) was Sir Thomas Molyneux; John
R. tells us that he was High Sheriff of Lancs in 1473 and died 12 July
1483.

Is the birthdate of Sir Thomas Molyneux known? I have seen it referred
to as "circa 1445". Is his father's IPM (c1459) available?

It could be instructive to compare his birthdate (and thus his mother's
latest birthdate, some twelve years earlier), with that of his maternal
uncle, Thomas, 1st Earl of Derby, who is apparently assigned a
birthdate of 1435.

(D) the children of Thomas, Earl of Derby, died 1504. His eldest son
was George (d 1497) but there was also at least one daughter, Margaret,
Lady Osbaldeston.

(E) is it known that Jane Stanley was George's first-born child?

Will, here's your chance to shine!!

MA-R

PS the website promoting these claims - which I consider worthless -
may be found here: