From Leo's Tree:
Of the twenty-five barons who were elected by their peers to be sureties to keep King John to the terms of the Great Charter, eight barons did not have descendants past the fourth generation. Of the remaining seventeen, I have discovered nine who are our ancestors.
The majority of the barons on the field at Runnymede were related to each other by blood or marriage. As previously shown by Roger and Hugh Bigod, some were father and son. So also are the next two - Richard and Gilbert de Clare. Again, we see for the eldest son, the label over the father's shield of arms.
Above are the arms for Sir Richard de Clare. His blazon is:
Or three chevrons gules
Sir Richard de Clare, Earl of Hertford, Lord Clare of Castle Tonbridge, Magna
Carta Surety Baron 1215, lived 1153-1217.
The arms for Sir Richard's eldest son Sir Gilbert de Clare are:
Or three chevrons gules a label azure
3rd Earl Gloucester, 7th Earl of Clare, Earl of Hertford, Magna Carta Surety Baron 1215, lived 1180-1230.