These include wish for her children to have relationship with siblings

But she will not accept any willing parents - they must adhere to terms

Now, she is taking to Facebook to find couple to adopt six extra embryos

She finally gave birth to two sets of twins, aged three and 16 months old

of dollars on IVF in a bid to conceive

She spent years of 'heartache' and thousands of dollars on IVF in a desperate attempt to conceive.

And in 2011, Angel Watts gave birth by a set of twins - followed by another set 16 months ago.

Now, the devoted mother-of-four is taking to Facebook in a bid to help another couple to achieve their dream of having children - by advertising her six unused, donated embryos for adoption.

However, she will not accept any willing parents-to-be - they must adhere to a list of what some may perceive as unusual terms that she has posted on the social networking site.

Mrs Watts, mother to Alexander and Shelby, aged three, and 16-month-old Angelina and Charles, says she wants the couple whom she chooses to be financially capable of supporting six children.

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Taking action: Angel Watts (pictured, far right, with her husband, Jeff, and two sets of twins, Alexander, Shelby, Angelina and Charles) is taking to Facebook to help another couple to achieve their dream of having children

They must also be in 'a steady, loving relationship' with 'a strong Christian background', good health (aside from infertility) and roots in Tennessee, where Miss Watts and her husband, Jeff, are from.

Perhaps most strikingly, the chosen couple must raise any children together and allow the Wattses to have a relationship with their biological siblings - unlike many embryo donation arrangements.

They should also not space the offspring too far apart in age - ideally, the majority of the embryos will be used over 'a six-year window', Mrs Watts, who lives with her family in Mount Juliet, says.

In her long Facebook post in December, Mrs Watts, whose embryos are in storage at the National Embryo Donation Center in Knoxville, said: 'We come with good news for someone out there.

Strict guidelines: However, the mother-of-four (pictured) will not accept any willing parents-to-be - they must adhere to a list of what some may perceive as unusual terms that she has posted on the social network site

Desires: Mrs Watts says she wants the couple whom she chooses to be financially capable of supporting six children. They must also be in 'a steady, loving relationship' with good health and roots in Tennessee

'We are seeking a couple in the area who has roots in TN who is having issues with infertility who are otherwise healthy and will need IVF in order to start a family.

ANGEL WATTS: WHAT THE PARENTS OF HER EMBRYOS SHOULD BE LIKE - A couple that wants a large family and can afford to have six children - They will ideally be in 'a steady, loving relationship' and have 'a strong Christian background' - They must have roots in Tennessee - Aside from issues with infertility, they should otherwise be healthy - 'No super age gap' between the siblings - ideally, most embryos will be used over 'a six-year window' - They must be 35 years old or younger 'in order to set the process up for the best odds of success' Advertisement

'We have 6 good quality frozen six-day-old embryos to donate to an amazing family who wants a large family. ... It would be very nice if there is no super huge age gap between the siblings.'

Speaking to USA Today, Mrs Watts said she decided to advertise her extra embryos - initially donated by a 20-year-old woman - after reading stories of ill-fated donor-conceived children.

Some of these children felt disregarded - by science and donor anonymity - from any chance of knowing anything about where they came from, she said.

In relation to her own children, she added: 'Sometimes, when they are playing together and doing their own thing, absorbed in their own little world, I feel like I could just watch them forever.

'I feel like I don't even need to watch television, that I could just watch them all the time.'

Doctor and lawyer Ellen Wright Clayton, of Vanderbilt University Medical Center, told the news site that some of Mrs Watts's terms were backed by scientific evidence.

She explained how the desires of donor-conceived children are not entirely different from those of adopted children.

Family: Speaking to USA Today, Mrs Watts (pictured with her family) said she decided to advertise her extra embryos - initially donated by a 20-year-old woman - after reading stories of ill-fated donor-conceived children

Further rules: Perhaps most strikingly, the chosen couple must raise any children together and allow the Wattses to have a relationship with their biological siblings - unlike many embryo donation arrangements

Mrs Watts said: 'We are seeking open communication and meetings so siblings grow up to know each other'

'There's tons of evidence to show that many, many people who are raised in families that weren't the ones who bore them want to know where they came from,' she said.

She added that there appeared to be nothing legally wrong about Mrs Watts donating the embryos.

Although the Wattses have received numerous responses to their Facebook post, they are yet to find a match.

Mrs Watts, 45, cannot carry the additional 'good quality' embryos herself due to her age and health.