My dearest Frank I wish you joy

My Dearest Frank, I Wish You Joy
by Jane Austen
Chawton, July 26--1809

My dearest Frank, I wish you joy
Of Mary's safety with a Boy,
Whose birth has given little pain
Compared with that of Mary Jane.--
May he a growing Blessing prove,
And well deserve his Parents' Love!--
Endow'd with Art's and Nature's Good,
Thy Name possessing with thy Blood,
In him, in all his ways, may we
Another Francis WIlliam see!--
Thy infant days may he inherit,
THey warmth, nay insolence of spirit;--
We would not with one foult dispense
To weaken the resemblance.
May he revive thy Nursery sin,
Peeping as daringly within,
His curley Locks but just descried,
With 'Bet, my be not come to bide.'--
Fearless of danger, braving pain,
And threaten'd very oft in vain,
Still may one Terror daunt his Soul,
One needful engine of Controul
Be found in this sublime array,
A neigbouring Donkey's aweful Bray.
So may his equal faults as Child,
Produce Maturity as mild!
His saucy words and fiery ways
In early Childhood's pettish days,
In Manhood, shew his Father's mind
Like him, considerate and Kind;
All Gentleness to those around,
And anger only not to wound.
Then like his Father too, he must,
To his own former struggles just,
Feel his Deserts with honest Glow,
And all his self-improvement know.
A native fault may thus give birth
To the best blessing, conscious Worth.

As for ourselves we're very well;
As unaffected prose will tell.--
Cassandra's pen will paint our state,
The many comforts that await
Our Chawton home, how much we find
Already in it, to our mind;
And how convinced, that when complete
It will all other Houses beat
The ever have been made or mended,
With rooms concise, or rooms distended.
You'll find us very snug next year,
Perhaps with Charles and Fanny near,
For now it often does delight us
To fancy them just over-right us.

I'm not sure she's saying a lot other than whats obvious in the text, it's simply part of a congratulatory letter written to her brother Francis (Frank) on the birth of his second child and intended as nothing more.

Mary was Frank's wife, and she means the birth went easily (the birth of the first child Mary Jane was painful and protracted - she was present at the time.)

She's also comparing the child to him a boy - peeking his head around the nursery door with the words "Bet, my be not come to bide!" meaning Bet, I've not come to stay - imitating the servants' dialect. She also says that she hopes that like his father he's as brave and frightened of nothing - except a donkeys' braying.

She also states she happy with her new home and hopes to see her relatives staying at Chawton Manor house just down the lane.