A pair of Indian Thumb gusset mittens custom fit to my husband’s hands. My own pattern (see below).

Pattern:

Cast on 42 sts.
Knit 1x2 rib (K2 P1) for 25 rounds (3”).
Knit 5 rounds plain stockinette.

Right mitt:
Mark the first 15 sts with a stitch marker. These will be the thumb stitches.
Start increasing stitches back into the palm by knitting past the marker and then kfb.
Increase this way on every round until there are 42 sts outside the thumb markers (57 sts total).
Knit 5 rounds plain until thumb gusset is long enough.

Next round: remove 15 thumb stitches and put then on a stitch holder. Cast on 2 stitches over the gap. 44 stitches total.

Knit plain until mitten reaches the top of the pinkie finger (26 rounds).
Start decreases: K9 K2tog around
Next round: Knit all stitches
Continue decreasing in this manner, every second round, until 20 stitches remain. Then decrease EVERY round until 8 stitches remain. Tie off top of mitten.

Left mitt:
Mark the last 15 sts with a stitch marker. These will be the thumb stitches.
Start increasing stitches back into the palm by knitting to one stitch before the marker and kfb in that stitch.
Increase this way on every round until there are 42 sts outside the thumb markers (57 sts total).
Knit 5 rounds plain until thumb gusset is long enough.

Next round: remove 15 thumb stitches and put then on a stitch holder. Cast on 2 stitches over the gap. 44 stitches total.

Knit plain until mitten reaches the top of the pinkie finger (26 rounds).
Start decreases: K2tog K9 around
Next round: Knit all stitches
Continue decreasing in this manner, every second round, until 20 stitches remain. Then decrease EVERY round until 8 stitches remain. Tie off top of mitten.

Thumb:
Put 15 held stitches on to double pointed needles. Pick up six stitches over thumb gap (21 sts). Attach yarn and knit first round, decreasing two of the picked up stitches out on first round (19 sts total).
Knit 13 rounds, then decrease one stitch (18 sts).
Knit one round plain.
Decreases:
Round 1: K4, K2tog 3 times (15 sts)
Round 2: Knit all stitches
Round 3: K3, K2tog 3 times (12 sts)
Round 4: K2, K2tog 3 times (9 sts)
Round 5: K1, K2tog 3 times (6 sts)

Cut yarn and draw through the remaining stitches.
Weave in ends.