Looking at the baptisms again I think it's probably the same family. Thomas and Charlotte baptised three children in Warwicks starting in 1742, then six in Meppershall, topping it off in Southill in 1768 with Decima, the tenth (except the baptism of the first child which is an IGI member submission so not to be relied on, the rest are extracted entries so are OK). A 26 year child bearing span is about right, and isn't at all out of the usual, so that causes me no concerns. What does worry me a bit is the 4 year gap between the alleged marriage in 1738 in Snitterfield (another member submission) and the baptism of the first son in Snitterfield in Dec 1742. What were they doing? And that pushes the span between marriage and Dulcima's baptism to 30 years, which is a push unless Charlotte was only 16 when they married, or if Dulcima was a late baptism by 3 or 4 years.
Thomas was baptised in Warwicks on 6 Mar 1747, so he was young if he married on 12 May 1763; only just 16. Again, not impossible though.
Member submissions on the IGI/Pedigree Resource files/online trees are all to be taken as guides only, with facts being checked against parish registers. That should be your next step, particularluy with the Warwicks marriages. We can all speculate as much as we like - it's what the parish register says that will prove or otherwise what we may hypothesise.
But logistically it's all a bit disjointed. Thomas & Charlotte moved from Warwicks to Meppershall some time between the baptism of Thomas junior in 1747 and 1750. Thomas jnr then moves back to Warwicks to marry a girl from Beds in 1763, has a kid there and then moves back to Southill, Beds. I would like to see the 1763 marriage entry to see if it says Sarah Warren of the parish of Yelden. My money is on no such statement! Member submissions on the IGI as well as that tree you quote on Pedigree Resource file give Sarah Warren's baptism as 16 June 1747, illegitimate dau of Elizabeth. It would be interesting to look at Yelden parish register to see what detail it provides about the burial on 25 June 1747 of Sarah Warren, nine days after the baptism. Cynical old xxxx I may be, but I suspect that the two events are connected, and the PR tree picked out a Sarah Warren that roughly fitted datewise, notwithstanding that she was from the wrong part of the country. Take online trees with copious helpings of salt.
David